Automatic safety device for internal combustion engines



L L. SCOTT 2,152,237 AUTOMATIC SAFETY DEVICE FOR INTERNAL COMBUSTIONENGINES March 28, 1939.

Filed April 8, 1 937 INVENTOR Le/ 0a A. 5602)? BY ATTORNEY Patented Mar.28, 1939 UNITED F F1 GE AUTOMATIC SAFETY DEVICE FORINTERNAL COMBUSTIONENGINES V Leland L. Scott, Kansas'City. Mo. "Application-April -s,1937,:SerialNo. 135,722

5 Claims.

Inaccomplishing these and other objects of the invention, I haveprovided improved details of structure, thepreferred' form er -Whichisillustrated in the: accompanying drawing, wherein:

Fig. 1 sis: a perspective 7 view of a magneto equipped :with: a safety::-device: constructed in accordance" with my invention.

Fig.2 is. alongitudinal vertical section through the magneto. andsafetydevice.

Fig; 3 is -.a cross. sectiomthrough the :safety .de'yiceon the line;3'3,:'F.'ig;i2.

:-Fig. :4. is. a' crosstsection'uthroughiv the safety ydeviceonthe1linei4--4'; Fig.2.

Fig.6 is av detail fragmentary viewof a modified contact arrangement.

Referring more in. detailutothezdrawing: l designatesa portion ofaninternal combustion engine equipped with a conventional :type v.magneto:2 for: supplying-an ignition current by which the fuel in, the cylindersis ignited.

.Themagneto includes acasingt-3 for housing .the armature 4 and adistributor mechanism 5 which times the points of ignition "in the re-:spective cylinders. The armature 4 is mounted on; spindles. Land 8'rotatably mounted in. bearingsa 9 .and .l I]. carried by .the casing.Thespin ..d1e '1. carries..a .gear. I meshing. with a suitable .drivegear ,on .the crankshaft of the engine to rotate the armature at adefinite speed.- relative .to. that of the engine. .Theudistributingmechanism is operated by a shaft l2 .extendin-gin parallel relation tothe axis of the armature and has its ends rotatably mounted inantiefriction bearings l3 and 14. The shaft I2 is driven in timedrelation with the armatureby a gear l5 thereon meshing with a gear 16 onthe spindle 8, so that it also is driven at a definite speed relative tothe speed of the motor. In order to secure the-gear 15, the end-of theshaft I2 is ordinarily provided -With-a shoulder I1 andis threaded as atl8 to --receivea-suitablenut (not shown.) to clamp the gearthereagainstinyassuring' positive operation :Of thesdistributing:mechanism. -The1magnetoiis alsoequipped with a circuit interrupterrlllthat K is grounded as at 20 to provide an intermittent current to thespark plugs of the engine.

The magnetothus described. is of a common type such=as used1 onairplanemotors and-like 5 engines and specifically forms no part of the presentinvention other thanaffording .a convenient-mounting for-myimprovedsafety device,

- now to be described.

As above. mentioned it is the purpose of the 10 safety devicetoautomatically'disrupt functioning of the ignition circuit when theengine has attained an excessive RIP. M. and is in'danger of runningaway caused by sudden release of the engine from its working load. Forexample,

when an airplane is infli'ghtg the engine isoften released fromitsWorking load due to loss of the propeller" from breakageor other causes,consequently-upon relief of itslload the speed of the engine increasesata rapid rate to cause ex- 0 cessive 'vibration. The speed and:vibraticn increase so suddenly"that,-before the pilot becomes aware ofthe'fa'ct, the-engine has shaken itself loose from its support or hascaused serious damage to the plane. notice the sudden racing ofthe-engine, tit is a physically impossible for him to manually-shut -offthe ignition before damage has resulted.

*The present invention forestalls disastrous resultsby automatically;grounding the= magneto current, or in case of the ordinary batteryignition, by automatically opening the battery circuit. This isaccomplished in the first instance by tripping a switch to closedposition-and in 1 the latter instance by tripping a switch to openposition, as now tobe described.

In the illustrated instance the safety mechanism is mounted directlyupon the magneto and. includes a bell-shaped housing 2| comprising-acylindrical base portion 22 and a cap portion 23 which may be formed ofinsulating material.

The base portion 22 includesa flange portion 24 cooperating with themagneto housing to enclose the gear |5.and issecured in positionbyfastening devices '25 extending-through openings" 26 in titheflange-portion and-iintosthreaded openings 21 in the magneto casing, asshown in Fig. -12. The oppositeend of the-portion 22 terminates'in aninwardly extending .flange 28. forming a 1seat.29 for:an annular flange'30 of the cap portion-23, :which is secured thereto by fasteningdevices 3|.

Mountedon the endjOf the shaft I2 is a governor carrier member 32including a cylindrical bcdy' '33; provided-with, an internal:cylindrical .socket? shaving; :threads 31 conforming to'the Evenshouldthe pilot 25 threads l8 on the shaft |2 to retain the carrierthereon and to take the place of the nut usually employed to clamp thegear l5 against the shoulder IT. The body of the carrier is slotted atopposite diametrical points, as at 38 and 39, and carries spaced ears 40and 4| extending radially from opposite side edges of the slots toaccommodate governor arms 42 and- 43 therebetween.

The governor arms include bell crank levers having hub portions 44pivotally mounted on pins 45 having their ends mounted in the cars 48and 4|. The outer arms 46 of the levers normally extend in parallelrelation to the axis of the shaft and carry governor weights 48 whilethe inner arms 49 extend within the socket 34 to engage the head 50 of atrip pin 5| which is slidably mounted therein and has its shank 52slidably mounted in the bearing opening 53 provided in the carrier inline with the axis of the shaft 2.

Sleeved over the shank 52 is a spring 54 having one end bearing againstthe head'50 and its opposite end against the bottom of the socket 34 tonormally urge the head against the arms of the bell cranks for retainingthe Weights in retractive position when the engine is operating atnormal speeds. The tension of the spring is, however, such as to allowthe weights to move the pin outwardly in the direction of the capportion 23 of the housing whenever the engine speed is such as to causethe centrifugal force of the weights to overbalancethe spring. It isthus apparent that whenthe engine begins to race or exceed its rated R.P. M. the weights will cause projection of the trip pin from the end ofthe governor carrier to trip' a switch mechanism now to be described.

The switch mechanism is carried by the cap section of the housing andincludes a fixed contact member 56 comprising a headed pin 51 having itsshank 58 extended through an opening 59 in the cap at a point spacedlaterally from the extended axis of the governor carrier. The shank 58isthreaded to receive a nut 60 to draw the contact head against its seat6| in the housing and to provide a terminal 62 for securing the groundwire 63 of the magneto which leads.

through a switch 64 in the cock-pit of the airplane for manuallydisrupting the ignition circuit by grounding the current generated bythe magneto when it is desired to stop operation of the engine.

' The switch mechanism also includes a contact plunger 65 having freesliding fit in a bearing opening 66 that is formed in the housing inline with the trip pin 5| and includes a cylindrical sleeve portion 61having a through bore 68 to slidably mount a control pin 69 and to housea spring 10.

The control pin 69 is backed by the spring 10.

which has its opposite end engaging the end H of an adjusting screw 12.The adjusting screw is threadedly mounted in the end of the borefarthest from the pin 5| and carries a lock nut 73 to engage the end ofthe contact plunger for locking the screw in adjusted position, as laterdescribed.

The outer end of the pin is retained by the spring 10 against an arm 14of a bell crank latch lever 15 that is pivotallymounted on a pin 16extending transversely of the housing below the plunger at a pointbetween the governor carrier and the contact plunger, as shown in Fig.2. The other arm 11 of the bell crank lever terminates in a hook 18 toengage a latch head 19 on the plunger, the latch head being cone-shapedto provide an inclined surface to guide the hook into latchingengagement with an annular shoulder 8| formed by the head. Also providedon the plunger is an annularly extending contact plate 82 arranged toengage the fixed contact member 56 but which is normally retained out ofengagement therewith by the latch lever.

It is, therefore, obvious that the hook on the latch lever is engagedwith the shoulder 8|, the arm 74 thereof being engaged by the controlpin and the spring 10 is retained thereby under tension to keep thelatch engaged for holding the contact plate out of contact with thefixed contact member 56.

In order to set the latch I provide a lever 83 pivotally mounted in aslot 84 in the casing on a pin 85 and which has one end 86 projecting inthe path of the contact plate and its opposite end 81 secured to aflexible cable 88 leading to the cock-pit of the airplane.

In using the device constructed andassembled as described, the spring I0is adjusted to the proper tension by manipulating the adjusting screw 12to resist action of the trip pin 5| until 4 the R. P. M. of the engineapproaches the danger point. The contact plunger 65 is then moved intolatching engagement with the latch lever 15 by pulling on the cable 88.This causes the end 86 of the lever 83 to engage the contact plate 82for moving the plunger 65 until the hook l8 rides over the head 19 andengages the shoulder 8|. The latch then retains the switch mechanism inset condition ready to be tripped by the trip pin 5| should the engineexceed a predetermined speed as set by the adjusting screw 12.

Under ordinary engine speeds, the pressure of themain spring 54 isenough to keep the trip pin from contact with the latch lever and thegovernor weights in retracted position. It is thus apparent that underordinary engine speeds, there are no moving parts subject to wear or toget out of adjustment but should the R. P. M. of the engine approach thedanger point, the centrifugal force caused by the increased rotationalspeed of the shaft 2 will cause the governor weights to move outwardly.This causes the governor arms to move the trip pin 5| against tension ofthe spring 54 until the end thereof engages the arm 14 of the latchlever. When the centrifugal force increases to overcome the resistanceof the spring 10 the latch lever is rocked to cause release of the latchhook 18, whereupon the spring 16 expands and acts against the end of theadjusting screw to move the plunger outwardly in its bearing and thecontact plate 82 into engagement with the fixed contact 56. This groundsthe magneto current through the plungor 65 and housing 2| to stopoperation of the engine in the same way as the manually operated switch64.

The pilot may re-establish the ignition circuit by pulling upon thecable 88 but if the cause of the excessive engine speed has not beenrepaired,

the safety device will. again function to stop is obvious that theignition circuit will be broken when the safety device functions;otherwise the construction will be identical to that shown in Figs. 1 to4.

While I have particularly described the safety device as being mountedon the magneto, it is obvious that it may be mounted uponany convenientrotating shaft of the engine without departing from the spirit of theinvention.

What I claim and desire to secure by Letters Patent is:

1. An ignition omitting mechanism for internal combustion enginesincluding a housing, a fixed contact carried by the housing and adaptedto be connected with an ignition circuit of an engine, a contact membermovable in the housing to and from contacting relation with the fixedcontact, a bell crank latch lever pivotally mounted in the housing andselectively engaging the contact member, trip mechanism in the housingengageable with an arm of said bell crank lever, a spring normallyretaining said bell crank latch lever in latching engagement with thecontact member and for urging said contact member into one positionrelatively to the fixed contact, and means responsive to speed of theengine for actuating the trip mechanism.

2. An ignition omitting mechanism for internal combustion enginesincluding a housing, a fixed contact carried by the housing and adaptedto be connected with an ignition circuit of an engine, a contact plungerslidably mounted in the housing and movable to and from contactingrelation with the fixed contact, a control pin slidable in the contactplunger, a bell crank lever pivoted in the housing and having alatch-shaped head engageable with the contact plunger and having an armengaged by said control pin, a spring normally urging the control pininto engagement with said bell crank arm to maintain said latchingengagement with the contact plunger and t yieldingly urge said contactplunger into one position relatively to the fixed contact upon releaseof-said latching engagement, trip mechanism in the housing for releasingthe bell crank lever, means responsive to speed for actuating the tripmechanism, and means carried by the housing for relatching the bellcrank lever with said contact plunger.

3. An ignition omitting mechanism for internal combustion enginesincluding a housing, a fixed contact carried by the housing and adaptedto be connected with an ignition circuit of an engine, a contact plungerslidably mounted in the housing and movable to and from contactingrelation with the fixed contact to control the efiectiveness of theignition circuit, a control pin slidable in the contact plunger, aspring in the plunger engaging the control pin, means threaded in thecontact plunger for tensioning the spring, a latch lever adapted toengage the contact plunger and .having an arm engaging the control pinto tension said spring, means for pivotally mounting the latch lever inthe housing, a trip mechanism in the housing adapted to engage the latchlever to release the contact plunger, and a governor adapted to beactuated by speed of the engine for operating said trip mechanism.

4. An ignition omitting mechanism for internal combustion enginesincluding a housing, a fixed contact carried by the housing and adaptedto be connected with an ignition circuit of an engine, a contact plungerslidably mounted in the housing and movable to and from contactingrelation with the fixed contact to control the effectiveness of theignition circuit, a control pin slidable in the contact plunger, aspring in the plunger engaging the control pin, means threaded in thecontact plunger for tensioning the spring, a latch lever adapted toengage the contact plunger and having an arm engaging the control pin totension said spring, means for pivotally mounting the latch lever in thehousing, a carrier member rotatably mounted within the housing, governorweights pivotally mounted on the carrier member, means adapted to beactuated by the engine for rotating the carrier member, and a springtensioned trip member slidable in the carrier member for normallyretaining the governor weights in retracted position but movable inresponse to movement of the governor weights to trip said latch lever torelease the contact plunger.

5. An ignition omitting mechanism for internal combustion enginesincluding a housing, a fixed contact carried by the housing and adaptedto be connected with an ignition circuit of an engine, a contact plungerslidably mounted in the housing and movable to and from contactingrelation with the fixed contact to control the effectiveness of theignition circuit, a control pin slidable in the contact plunger, aspring in the plunger engaging the control pin, means threaded in thecontact plunger for tensioning the spring, a latch lever adapted toengage the contact plunger and having an arm engaging the control pin totension said spring, means for pivotally mounting the latch lever in thehousing, a carrier member rotatably mounted within the housing, governorweights pivotally mounted on the carrier member, means adapted to beactuated by the engine for rotating the carrier member, a springtensioned trip member slidable in the carrier member for normallyretaining the governor weights in retracted position but movable inresponse to movement of the governor weights to trip said latch lever torelease the contact plunger, and manual means carried by the housing forresetting the latch lever.

LELAND L. SCOTT.

